The present invention relates to communications, and, more particularly, to communication networks.
Communication networks may use different types of communication media based upon their deployment and service requirements. Two examples of communication media commonly used in networks are copper lines and fiber optic cables. Copper networks are characterized by generally low cost transmitters and receivers, but typically provide relatively low transmission speeds. Copper is often used as a communication medium when relatively short distances are involved and relatively low bandwidth is required. Conversely, fiber optic networks are characterized by generally higher cost optical transmitters and receivers, but typically provide relatively high transmission speeds. Fiber is often used as a communication medium when relatively long distances are involved and generally high bandwidth is required.
FIG. 1 illustrates a conventional network model in which a network element device 100 is coupled to a customer equipment device 105 via a communication medium 110. The communication medium may be, for example, a fiber optic cable or a copper wire. In addition, the network element 100, the customer equipment device 105, and the communication medium 110 may comprise part of a network, such as an Ethernet network. The network element device 100 and the customer equipment device 105 may each comprise a communication protocol module 200 as shown in FIG. 2 to implement the Ethernet communication protocol. Ethernet is based on a layered communication protocol model that comprises a physical layer, a data link layer, and higher level protocol layers.
The physical layer comprises a physical coding sublayer (PCS) 205, a physical medium attachment (PMA) sublayer 210, and a physical medium dependent (PMD) sublayer 215, which provides an interface to the physical communication medium 220. The PCS 205 is the sublayer that provides a uniform interface to the data link layer. The PCS 205 provides coding in which 8 bits are represented by 10 bit code groups, which comprise both data symbols and control symbols. The PCS 205 also generates carrier sense and collision detect indications and manages the negotiation process by which the network speed and mode of operation, e.g., full or half duplex, are determined. The PMA sublayer 210 allows the PCS 205 to support various types of serial, bit-oriented physical media by serializing code groups for transmission and de-serializing bits received from the physical medium 220 into code groups. The PMD sublayer 215 defines the physical layer signaling used for various media and defines the physical attachments for different media types.
The data link layer comprises a logical link control (LLC) sublayer 225, a media access control (MAC) sublayer 230, and a reconciliation sublayer (RS) 235. The RS 235 maps a carrier present status signal and an absence of collision status signal into physical signaling primitives that are understood by the MAC sublayer 230. The interface between the data link layer and the physical layer may be a media independent interface (MII) to allow any physical layer to be used with the MAC sublayer 235. Thus, the physical layer may be tailored for a particular physical medium and a particular data rate.